Whether you're an advanced Photoshop user or you'd rather work with a basic graphics program, converting photos to Warhol's silkscreen style is relatively straightforward. I'm using Photoshop for this shot, but the same principles apply to almost any image-editing program. Look around in yours and your bound to find the same sorts of features and filters.
There are two primary parts to every Warhol silkscreen: The bright solid colors and the black lines and details. True Warhol silkscreens didn't really have Benday dots-the printing dots that make up offset prints-but the look is appropriate for creating the feel of pop art, and putting your own spin on Mr. Warhol's work.
Step 1: Laying the foundation. Open the photograph you want to work on, and figure out what you want to see in the finished image since the silkscreen look is short on detail. For a portrait, for example, cut the subject out of the background and paste it on a new layer (leaving the original intact for later reference). Desaturate the layer to remove the color, and create a new layer (behind the isolated subject) filled with a solid color; this will be the background. Now you're ready to move to the newly clipped subject layer and turn it into a graphic pattern.
Step 2: Simplifying the graphics. Using any tool that will allow you to convert the grayscale subject into purely graphic black and white (such as levels, curves, threshold or even contrast-whatever you're most comfortable with) adjust the layer until it looks like a basic black and white impression of your subject. You can stop here and move on to the colorizing, or continue to create printing dots and add them to the photo. For the dots, copy the layer to a new document and convert it to a bitmap. In the bitmap dialog (found in the Image>Mode menu), adjust the dot pattern size and shape (I like round dots) until it looks pixilated-you'll know when it looks just right.
Copy and paste that layer back onto the original file, and set the layer properties to darken; this will remove the white part of the layer and leave only the black dots. Add another empty layer behind the halftone and control click the layer icon of the original isolated subject layer to create a selection of the subject's outline. Fill that outline with white-or a pertinent color for the bulk of your subject-and it's time to add the colors to the rest of the photo.
Step 3: Colorizing. For every color you'll add, create a new layer under the black detail. You may want to toggle the original on and off to see the subject in its original state, and to even choose colors that come straight from the original. For golden hair, for example, choose a color from the original and select an area to fill. For bright blue eyes, select the appropriate area and paint the new layer. Continue the process until the basics are colorized. (Depending on your skill level, you can also utilize fill layers or layer masks to put the colors exactly where you want them.) Remember-Warhol's silkscreens are simple. A few colors should be more than enough. Adjust the opacity of each layer as necessary to control the intensity of the color, as well as the detail on the black layer. Once the colors are in place, your silkscreen is practically done.
Step 4: Add the finishing touches. You may want to consider putting detail or patterns back into the background, or even duplicate the image and change colors to make diptychs and triptychs and quads-as Warhol did with his iconic images of Elvis Presley and Marilyn Monroe. The real last step is also the most fun: find a gallery, hang your art and prepare for your own 15 minutes of fame!